Quantitative proteomics profiling reveals activation of mTOR pathway in trastuzumab resistance
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Wenhu Liu1,2,3, Jinxia Chang4, Mingwei Liu2, Jiangbei Yuan1, Jinqiang Zhang1, Jun Qin2,5,6, Xuefeng Xia1 and Yi Wang2,5,6
1School of Pharmaceutical Sciences and Innovative Drug Research Center, Chongqing University, Chongqing 401331, China
2State Key Laboratory of Proteomics, National Center for Protein Sciences, Beijing Proteome Research Center, Beijing 102206, China
3School of Pharmacy, North Sichuan Medical College, Nanchong 637007, China
4School of Basic Medical Sciences, North Sichuan Medical College, Nanchong 637007, China
5Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
6Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
Xuefeng Xia, email: [email protected]
Yi Wang, email: [email protected]
Keywords: HER2, trastuzumab resistance, mTOR signaling pathway, gastric cancer, LC-MS/MS
Received: March 02, 2017 Accepted: April 12, 2017 Published: April 25, 2017
Trastuzumab is an antibody-based therapy drug targeting HER2-overexpressing tumors. While it has been proven to be very successful initially, most patients eventually develop resistance to trastuzumab. The mechanism of drug resistance is not well understood. Identifying pathways that mediate trastuzumab resistance will improve our understanding of the underlying mechanism and is crucial for the development of therapeutic strategies to overcome resistance.
Here we report a quantitative proteomics profiling of a trastuzumab-sensitive (T-S) gastric cancer cell line NCI N87 and a trastuzumab-resistant NCI N87 (T-R) subline generated by low-dose, continuous trastuzumab treatment. By identifying proteins differentially expressed in these two cell lines, we show that multiple pathways including mTOR, Wnt, DNA damage response and metabolic pathways are significantly altered. We further confirm by western blotting that protein levels of multiple components of the mTOR pathway, including mTOR, AKT and RPS6KB1, are increased, whereas AKT1S1 is decreased, suggesting the activation of mTOR pathway. Importantly, treatment of AZD8055, an mTOR inhibitor, leads to the decreased phosphorylation levels of mTOR downstream molecules RPS6KB1 at Thr421/Ser424 and AKT at Ser473. Furthermore, AZD8055 also preferentially reduces viability, and inhibits migration and invasion abilities of the T-R cells. Together, our findings indicate that mTOR pathway is among multiple signaling pathways that mediate trastuzumab resistance in NCI N87 T-R cells, and that mTOR inhibitors may be used to treat trastuzumab resistant, HER2-positive gastric cancer tumors.
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